Biomedical subjects
Publications and source records attributed to M Gebhart.
A giant solitary osteochondroma of the proximal humerus in a 9-year-old boy was widely resected. Reconstruction of the bone defect was achieved with two nonvascularized fibula segments which gave sufficient stability to the proximal humerus and yielded rapid bone remodeling into an almost normal cortical bone after six months.
Repair of large bone defects represents a challenge to orthopedic surgery since autogenous graft is not available in large amounts. Demineralized bone matrix (DBM) which contains bone morphogenic protein, a potent osteoinductive glycoprotein, and collagen, an osteoconductive matrix, may be an effective substitute for these graft materials. Bone marrow which contains osteoprogenitor cells could potentiate the osteoinductive and osteoconductive properties of demineralized bone matrix. This study tested the ability of demineralized bone matrix with and without bone marrow to bridge large segmental defects, and evaluated the results both radiographically and biomechanically as compared to autogenous (isogeneic) cancellous bone graft. Demineralized bone-matrix segments implanted into a plated femoral segmental defect in rats resulted in firm union in most animals. Bone marrow significantly enhanced bone formation of demineralized bone-matrix implants at an early stage but with time, differences between bone marrow-augmented and bone marrow-deprived demineralized bone implants were no longer demonstrable radiographically and biomechanically. Newly formed bone had about 50% of the strength of the contralateral control bones. Femurs implanted with cancellous bone isografts had similar evidence of absolute union rate, radiographic and mechanical properties as DBM-implanted femurs.
Six patients who had undergone an en bloc interscapulo-thoracic excision (for primary bone or soft tissue sarcoma in five, and metastatic disease in one) were subject to review, with special emphasis on the functional outcome of the operated arm. Active shoulder motion was poor in all patients, but this did not prevent passive positioning of the hand and elbow. Elbow and particularly hand function was either not, or only slightly, impaired so that two patients regained full use of their upper extremity. Three patients had satisfactory but impaired function and one with metastatic disease of the should had a poor functional outcome.
Out of a total of 31 patients (26 females and five males) there were 24 complete and nine impending pathological fractures. These, treated from October 1985 to September 1987 at the Bordet Institute, were evaluated. Breast cancer was the most frequent underlying disease (66%) followed by lung cancer (12%). Eighteen lesions were treated by endoprosthetic replacement and 15 by an intramedullary fixation device. Bone cement was added to either of these. Satisfactory pain relief was obtained in 82% of the treated areas and restoration of function in 76%. Complications were rare but included one easily resolved superficial wound infection, four deep venous thromboses, movement limited to 21% (seven joints), and the changing of two fixation or reconstruction devices. Median survival time was 6 months; 35% of the patients were still alive after 12 months and 10% after 24 months.
The Van Nes rotation plastic surgery technic is a procedure to lengthen the femoral stump. It is used for patients with an immature skeleton who present a malignant bone tumour around the knee. The operation is an alternative to high transfemoral amputation. Nine patients treated with this procedure are reviewed. In five surviving patients, characteristics of walking, extension strength of the foot, and early and late complications were satisfactory.
Very large bone and soft tissue tumors located in the pelvis or upper thigh may require hemipelvectomy if local excision is not possible. Classical hemipelvectomy is associated with a high risk of local complications and usually with a poor functional result. This paper describes a modified hemipelvectomy where the preservation of the upper iliac wing provides a counterpressure for the external prosthesis, and a vascularized anterior musculo-cutaneous thigh flap decreases the risk of skin necrosis and wound problems.
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Ewing's sarcoma occurs most often in young males of caucasian type and affects the medio-diaphysis of a long bone of the lower extremity, the pelvis and the humerus. Radiologically there is bone destruction, onion skin appearance, a Codman triangle and extension into the surrounding soft tissues. Microscopically, this tumor is composed of small round cells and it can be differentiated from non Hodgkin lymphoma, metastatic neuroblastoma and embryonal rhabdomyosarcoma. Recent immunological studies suspect a neuroectodermal origin. Ewing's sarcoma growths rapidly and spreads to lung and other bone locations. Without treatment, survival at 5 years is less than 5%. The actual therapeutic approach is multidisciplinary including surgery, chemotherapy and if necessary radiotherapy. With this approach actual survival rates at 5 years reaches 75%.
Two cases of either cervical or acetabular osteoradionecrosis were described. One patient had endoprosthetic replacement of the hip, the other did not receive any surgical treatment. Regarding the literature, osteoradionecrosis occurs in 0.3 to 4% of the irradiated bones. Histologically there is a destruction of the bone by direct toxicity of the radiation and by destruction of the vascular supply. The threshold of irreversible bone destruction is 30 Gy. Fractures are epiphenomenons of osseous radionecrosis. The diagnosis can be suspected either by radiographies or by bone scans. Sometimes a bone biopsy is necessary to differentiate between bone necrosis, bone metastasis and eventually a radiation-induced sarcoma of the bone. If the osteoradionecrosis affects the acetabulum, even in the case of a stress fracture without acetabular protrusion of the femoral head, no surgical treatment is recommended. Weight bearing is avoided and spontaneous resolution occurs in most cases. If, on the other hand, there is a fracture through the femoral neck, hemiarthroplasty or total joint replacement is the treatment of choice. Total joint replacement is also recommended in case of an extensive radiation induced coxopathy.